Regulation of endothelial cell chromatin availability and transcription factor activity in arterial-venous specification - HUVEC FUCCI RNAseq

Arterial-venous specification of endothelial cells during vascular development requires coordination between intracellular signaling, cell cycle state, and transcription factor activity. However, the intrinsic regulatory mechanisms that govern these processes are poorly understood. To investigate this, we assessed endothelial chromatin accessibility during vascular development. Murine postnatal day (P)6 and P15 retinal endothelial cells were analyzed by single cell Assay for Transposase Accessible Chromatin (ATAC) sequencing, revealing heterogeneous accessibility of chromatin across an arterial-venous continuum. Enhancer regulatory network analysis predicted transcription factors with high activity, including Sox17. Transcription factors with differential arterial-venous activity showed dual activator and repressor functions, with many regulated by cell cycle-dependent chromatin accessibility. We validated SOX17 function in human endothelial cells, identifying that SOX17 inhibits proliferation and promotes arterial gene expression. Our findings suggest that dual roles of key endothelial transcription factors are regulated by chromatin accessibility in a cell cycle- and subtype-specific manner to control arterial-venous specification.